Composition analysis of natural gas in the presence of liquid impurities by high-pressure proton low-field Nuclear Magnetic Resonance spectroscopy

• High-pressure 1 H NMR spectroscopy for analysis of liquid/gas mixtures up to 200 bar. • Composition analysis of natural gas samples in the presence of TEG as liquid impurity. • NMR experiments in the presence of static and dynamic TEG possible. • Quantification of TEG amount under static conditions. • NMR composition of the ternary gas sample in agreement with the vendor certificates. Natural gas (NG) plays a key role in the transition to greener energy sources. Accurate composition analysis is essential for determining NG’s commercial value and ensuring efficiency across the entire value chain. Since NG typically contains water, it is dehydrated using agents like triethylene glycol (TEG). However, residual liquid TEG may remain in the pipeline, compromising sample quality for conventional NG composition analysis, which can measure only the gaseous phase. Thus, this work demonstrates the applicability of high-pressure (HP) benchtop 1 H NMR spectroscopy for analyzing wet NG, with the simultaneous detection of gas and liquid phases. To enhance the robustness of the method, additional quality control parameters (QC) for the NMR signal were implemented alongside with previously established QCs. The methodology was validated using a three-component NG sample at 200 bar, in the presence of TEG as dynamic droplets and at varying stationary amounts within the sensitive volume. The determined NG composition was in excellent agreement with the vendor certificate. Moreover, the detection and quantification limits of TEG under the employed experimental conditions were determined. This work represents a significant step towards the integration of HP benchtop NMR spectroscopy for real-time monitoring of wet NG composition in industrial environments.